This application claims the priority of U.S. Provisional Application No. 61/287,749 filed Dec. 18, 2009.
The present disclosure relates to a vision aid for patients with age-related macular degeneration (AMD) and other low vision conditions, including amblyopic patients. AMD patients usually have impaired central visual fields and often rely heavily on peripheral vision for daily tasks. Generally, the peripheral retina has low receptors densities relative to the central retina, which leads to a lower resolution ability. Low vision patients, such as those with AMD, also have poor central retina resolutions. In that regard, AMD patients often have compromised fovea. However, there are typically still functional retina receptors surrounding the compromised central receptors. These functional retina receptors are often peripherally located and have larger spacing between each other. The increased spacing results in a decreased image resolution. For example, at 3 degrees nasal retina, the visual acuity is reduced to 0.4 compared to the 1.0 visual acuity at 0 degrees, and at 5 degrees nasal retina, the visual acuity is reduced to 0.34 compared to the 1.0 visual acuity at 0 degrees.
Currently, there are three basic types of vision aids available for patients with low vision conditions. The first type is a single telescope. The single telescope is often mounted on the spectacles, which are heavy and are not appealing cosmetically. Implanted telescopes often require very large incisions during surgery to implant. The main disadvantages of using a telescope system are that the resultant visual field of view is narrowed and the overall image quality is poor. The narrow field of vision, or tunnel vision, creates a safety concern for the patient. In that regard, the narrow field of vision prevents the patient from recognizing movements that would normally be seen in the peripheral vision. Since the patient cannot see the peripheral movements, the patient will not react to those movements, which can potentially lead to patient injury.
The second type of vision aid is a prism. The prism is utilized to realign the line of sight to the peripheral retina. However, the prism must overcome a binocular fusion problem in order to avoid double imagery. Further, the prism does not magnify retinal images. So, the problem of low visual resolution caused by the larger peripheral retina receptor spacing cannot resolved with the prism.
The third type of vision aid is a magnifying glass. In some instances, the magnifying glass is combined with a prism. The magnifying glass is often used as a desk mount device, which limits the useful range of the device for patients. A handheld magnifying glass, while being portable, is not suitable for many elderly patients that have hand tremors because of the resulting vision instability and focus problems.
Therefore, there remains a need for improved vision aids for the low vision population, including patients with AMD.